Meanwhile, trim 1-inch off the end of each sweet potato. Using the V-slicer or mandoline, slice the sweet potatoes into very thin slices, about 1/8-inch thick. Trim 1-inch off the root end of the beets. Using the V-slicer or mandoline slice the beets into very thin slices, about 1/8-inch thick.

When the oil is hot add about a quarter of the sweet potato slices. Let fry until golden and the bubbling has almost completely subsided, about 2 to 3 minutes. Using a mesh sieve or slotted spoon remove the chips to a paper-towel-lined baking sheet. Sprinkle with some of the garlic, rosemary, and salt mixture. Continue with the remaining sweet potatoes.
Transfer to a serving plate.

Next, fry 1/4 of the beets. Let fry until curled at the edges and most of the bubbling has subsided, about 3 to 4 minutes. Transfer the beets to another paper-towel-lined baking sheet and sprinkle with salt mixture. Continue with the remaining beets. Let cool and transfer to a serving plate.